Syringe construction having internal bladder



United States Patent Inventor Harry K. De Witt Winnetka, Illinois Appl. No. 617,388

Filed Feb. 20, 1967 Patented Sept. 8, 1970 Assignee American Hospital Supply Corporation Evanston, Illinois a corporation of Illinois SYRINGE CONSTRUCTION HAVING INTERNAL BLADDER 8 Claims, 5 Drawing Figs.

US. Cl 128/218, 128/272 Int. Cl. A61m 5/18 Field efSearch 128/215,

216, 218/(N); (R), (M), 218.1, 272; 222/107, 215

[56} References Cited UNITED STATES PATENTS 770,215 9/1904 Blatz et a1. 222/107X 3,093,133 6/1963 Everett 128/216 3,158,155 11/1964 Myerson et al. 128/215 3,166,070 1/1965 Everett 128/218 3,424,155 1/1969 Sarnoff 128/218 FOREIGN PATENTS 1,364,894 5/1964 France 128/218 Primary Examiner--Richard A. Gaudet- Assistant Examiner-Gerard F. Dunne Attorney Dawson, Tilton, Fallon and Lungmus ABSTRACT: A hypodermic syringe having a re-usable barrel and plunger and having a disposable needle-hub-bladder assembly, the bladder being formed of highly stretchable and contractable material and being constructed and arranged to assume an untensioned state spaced inwardly from the sides of the barrel and in a relatively small zone immediately adjacent the needle hub.

Patented Sept. 8, 1970 HARRY K. DEWITT ATT'YS SYRINGlE. CONSTRUCTION HAVING INTERNAL BLADDER BACKGROUND OF THE INVENTION In recent years disposable hypodermic syringes have come into increasingly widespread use because they obviate the need for re sterilization and because they eliminate the problems which might otherwise arise should a reusable syr' inge be insufficiently cleaned and re-sterilized prior to use. However, the cost advantages of eliminating the time-consuming steps of cleaning and re-sterilizing syringes are largely offset by the fact that such disposable syringes are discarded after only a single use. While the cost of a disposable plastic syringe is considerably less than that of a re-usable glass syringe, the cost of the disposable unit when considered in terms of its extent of use is in many cases still prohibitively high.

Since the more expensive components of any syringe are its barrel and plunger, especially in view of recently-developed techniques or manufacturing relatively inexpensive needle and hub assemblies, efforts have been made to develop a satisfactory syringe which permits retention of the barrel and plunger for re-use, the disposable items being only the needle and its integrated hub. A collapsible bag composed of a thin film of plastic material is sealed to the hub and serves as a barrier to protect the interior of the barrel from direct contact with the injection fluid. Contamination during subsequent use is prevented since only the disposable portion, the needle-hubbag assembly, contacts the medicament and the patient and that assembly is discarded after use.

To insure proper filling of the plastic bag as the syringe plunger is withdrawn it has been found necessary to provide an aperture in the inner end of the plunger so that the collapsed, axially-elongated bag can be fully received within the hollow plunger. Then, as the plunger is pulled outwardly to draw medicament into the bag, the bag fills only in those portions played out from the axial cavity of the withdrawing plunger. In other words, the bag fills first in that portion nearest the needle and is filled only at its distal end when the plunger is drawn outwardly beyond the limits of the bag. Injection of the medicament is then achieved simply by returning the plunger to its original position, the head of the plunger bearing against the bag and its contents and forcing such contents outwardly through the cannula or needle.

While such a construction appears to solve one problem, it actually creates another which is severe enough to limit greatly the practical value of a bag-equipped syringe. The specific problem is that once the contents of the bag have been expelled from the syringe the bag cannot be re-filled with medicament or other fluid. It has been found that the collapsed bag blocks the orifice of the hub, clings to the sides of the barrel, and prevents return ofthc plunger to its outwardlyextended position. Since modern clinical technique generally requires two successive reciprocations of a syringe plunger, the first to charge a vial of medicament with a quantity of air to create a positive pressure within the vial, and the second to draw and inject the medicament, a syringe having a bag capable of only a single filling (with air, medicament, or any other fluid) has only very limited value.

SUMMARY OF THE INVENTION The structure ofthe present invention overcomes the aforementioned problems of prior disposable needle constructions by providing a bladder formed of highly stretchable and elastic material which is constructed and arranged to draw inwardly away from engagement with the walls of the syringe barrel as the contents of the bladder are discharged through the lumen of the needle. The bladder expands into the barrel as the syringe plunger is shifted outwardly, stretching to conform generally with the cavity defined by the barrel and plunger end, and recovers its original untensioned and generally unfolded state when its contents have been discharged and the plunger has been returned to its original position. In its normal untensioned position, the elastic bladder takes the form of a single layer or membrane covering the aperture at the dispensing end of the syringe barrel.

Since the bladder is capable of recovering its original compacted condition after being highly stretched, and since it is dimensioned to be spaced inwardly from the side walls of the barrel when the bladder is in an untensioned state, the plunger may be reciprocated two or more times without encountering interference from the bladder. In keeping with modern clinical practice, the syringe may be manipulated to inject air into a vial of medicament to create a positive pressure within that vial, and may then be operated again to draw medicament from the pressurized vial and to inject such medicament into a patient. After such use, the needle-hub-bladder assembly is simply detached and discarded, and the barrel and plunger, which constitute the major components of the syringe and which have not been directly exposed to the medicament or other fluid, are retained for re-use.

Other advantages of the present invention will be obvious to persons skilled in the art from the following detailed description ofa preferred embodiment accompanied by the attached drawing in which like reference numerals refer to identical parts in the various views.

THE DRAWINGS FIG. 1 is a perspective view of a hypodermic syringe construction embodying the present invention;

FIG. 2 is an enlarged fragmentary longitudinal sectional view illustrating the relationship of parts when the bladder is in a substantially untensioned state;

FIGS. 3-5 schematically illustrate a typical application of the syringe of FIGS. land 2.

DESCRIPTION As shown in FIG. 1, the syringe includes an elongated cylindrical barrel 10 having a circular or annular cross section and defining a discharge opening 11 at one end and a plungerreceiving opening 12 at its opposite end. The cylindrical barrel extends inwardly at 13 to define a reduced tapered section 14 about discharge opening 11. The tapered section 14 is frictionally received within the hub of a needle-bladder assembly generally designated by numeral 15.

At the plunger-receiving opening of the barrel are a pair of finger-support flanges l6 and 17 which project outwardly from diametrically opposite sides of the barrel. The barrel is also conventional provided with graduation indicia, as illustrated at 18 in FIG. 1.

A plunger 19 is slidably received within the tubular cavity 12 of barrel 10. In the illustration given, the plunger comprises a thumb pressure cap 20, a shank portion 21 extending from the thumb cap and dimensioned for axial movement within barrel I0, and a plunger head 22 affixed to the proximal end of the shank and provided with sealing rings 23 and 24 spaced axially apart for sealingly and slidably engaging the interior wall surface of the barrel. The leading portion of the plunger head is provided with an enlargement 25 which, upon full insertion of the plunger into the barrel, will fit within the reduced portion 14 to discharge medicament which might otherwise remain therein.

The barrel and plunger are preferably formed from transparent plastic materials of the type now commonly employed for hypodermic syringes although, in view of the fact that these parts are not intended to be discarded after a single use, other materials such as glass might be used. Thus, the quality of material and construction of barrel 10 and plunger 19 may be well above the levels found in conventional disposable syringes without affecting the relatively low-cost economy in herent in the use of the syringe construction of the present invention.

The needle-bladder assembly 15 includes a hub or reducing nipple 26 which centrally receives a conventional hypodermic needle 27. The enlarged end of the hub defines a cavity 28 which accommodates the reduced portion 14 of syringe barrel 10. An annular ridge 29 is formed internally of the cavity 28 adjacent its open end. A highly stretchable and elastic bladder 30 is disposed within cavity 28 and, in the illustration given, has its peripheral edge portions secured to the inside side surfaces of the cavity by means of an annular retaining ring 31. As shown in FIG. 2, ring 31 is locked within the cavity by ridge or flange 29 and presses outwardly against the peripheral portion of the bladder to hold that portion tightly in place. If desired, a suitable cement or other adhesive material may be used to assist in sealing the peripheral skirt portion of the bladder to the hub. However, for most applications such adhesive interconnection is believed unnecessary because of the cooperative relationship of the parts which results in a tight wedging of the bladders skirt portion against the side wall of the hub. It will be observed that when the hub is pressed on to the tapered section 14 of the barrel, the annular retaining ring 31 is forced into radial expansion to further increase the wedging and locking forces applied to the peripheral portion of the bladder.

In its untensioned state, the thin, highly resilient bladder is disposed within cavity 28 and is retracted inwardly from surface contact with the inner side walls of the barrel. Furthermore, since the bladder is formed of elastic material, the word elastic here being used to mean a highly stretchable material which will return to its original contracted condition after stretching forces have been discontinued, the bladder will tend to draw inwardly away from the side walls of the barrel, and will assume its normal state spaced inwardly from such side walls, whenever it is returned to its untensioned condition. In such normal untensioned condition, the bladder, while it may have some slack (FIG. 2), is substantially free of any folding or doubling over of material.

The elasticity of the bladder or membrane 30, when in stretched condition, creates a positive pressure on fluid disposed within the bladder (between the bladder or membrane and needle 27) and a negative pressure outside of the bladder (between the bladder and the plunger within barrel 10). The extent of this negative pressure depends largely upon the retractive force exerted by the bladder itself in attempting to return to its untensioned state of reduced volume.

The material used in the construction of the bladder may be any highly stretchable and elastic material such as, for example, latex rubber, or the like. Plastic materials other than rubber which have similar characteristics of stretchability and elasticity may also be used and would be preferred in those instances where storage conditions or the chemical compositions of reagents might have some deleterious effect upon natural or synthetic rubber.

OPERATION As previously indicated, liquid medicaments are conventionally marketed in hermetically sealed containers or vials of the type generally indicated in FIGS. 4 and by reference numeral 35. Such a container is provided with a puncturable cap 36. In order to facilitate withdrawal of medicament 37 from container 35, an operator first partially withdraws or retracts a syringe plunger 19 from its barrel to create a negative pressure on the bladder 30 and to draw air into the bladder through needle 27.

With the stretched bladder filled with air, the operator then inserts needle 27 into vial 35 through the puncturable membrane 36 and then pushes plunger 19 into the barrel of the syringe to collapse the bladder and to force the trapped air from the syringe into the vial (FIG. 4).

When the plunger is again withdrawn to its retracted position, as illustrated in FIG. 5, the medicament is drawn from the, vial into the bladder, assisted by the positive pressure previously created in the vial. The medicament is then dispensed from the syringe by again pushing the plunger inwardly. It is to be understood, of course, that before any application of the medicament to a patient, whatever minute amount of air may have been drawn into the bladder with the medicament must first be expelled by advancing the plunger a short distance inwardly while the syringe is held with the needle in raised position.

The positive pressure exerted upon the medicament within the bladder by the reason of the elasticity of that bladder contributes to the ease of hypodermic injection. Since such positive pressure is accompanied by a negative pressure within the barrel of the syringe and outside of bladder 30, the pressure and rate of injection is easily controlled by manipulation of the plunger. It is important to note, however, that in normal operation of the syringe the bladder does not occupy all of the space between the hub and the plunger. As shown in FIGS. 3- -5, a small but definite spacing 38 is disposed between the bladder and plunger, at least until the contents of the bladder have been fully discharged and the end of the plunger abuts the membrane-covered inner end wall of the hub 26.

As the contents of the bladder are discharged, the retracting and contracting bladder 30 pulls inwardly and axially away from the inner side surfaces of barrel 10 well in advance of plunger 19. Even where considerable force is applied to the plunger to increase the rate of discharge of the contents, the material of the bladder cannot become caught between the sealing ribs 23 and 24 of the plunger and the inside surface of the barrel because of spacing 38 and because of the elasticity and contractability of the bladder. Consequently, the syringe may be repeatedly filled and emptied without danger of jamming or damaging contact between the plunger and bladder.

After use of the syringe, the relatively inexpensive needlebladder assembly 15 is simply removed from the end of the barrel and discarded. The barrel and plunger, which have made no direct contact with any injection fluid, will normally be retained for re-use.

While in the foregoing l have described an embodiment of the invention in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied without departing from the spirit and scope ofthe invention.

Iclaim:

1. In a hypodermic syringe having an elongated cylindrical barrel with a plunger-receiving end and a dispensing end and having a plunger slidably and sealingly disposed within said barrel, the combination with said barrel and plunger of a disposable needle-bladder assembly removably mounted upon said barrel at the dispensing end thereof, said assembly comprising a needle-equipped hub defining a cavity therein, and a highly stretchable and elastic inflatable bladder having its peripheral portion secured to said hub and defining an expandable chamber communicating with said needle, said bladder being so dimensioned as to be normally disposed substantially entirely within said cavity of said hub and spaced inwardly from the inside wall surfaces of said barrel and to be expandable axially away from said hub upon retraction of said plunger, said stretchable bladder being retractable inwardly away from the side walls of said barrel in advance of said plunger when said plunger is urged towards said hub.

2. The structure of claim 1 in which said barrel is provided with a reduced section adjacent said dispensing end and wherein said hub fits over and about said reduced section, the peripheral portion of said bladder being secured to said hub laterally of said reduced portion of said barrel.

3. The structure of claim 2 in which said reduced portion of said barrel is tapered and is frictionally received within the cavity of said hub, the peripheral portion of said bladder being subjected to compressive locking forces when said hub is fitted tightly upon said barrel.

4. The structure of claim 1 in which said bladder and plunger are spaced axially apart.

5. The structure of claim 1 in which said plunger has a smooth imperforate transverse end surface facing the dispensing end of said barrel.

6. A hypodermic syringe including a re-usable barrel of cylindrical shape and a re-usable plunger slidably received within said barrel and having an imperforate end sealingly engaging the barrels interior wall, wherein the improvement comprises a disposable needle-bladder assembly consisting essentially ofa hub having a first opening removably attached to said barrel and a second opening for receiving a needle, a needle secured to said hub in said needle-receiving opening, and a highly stretchable and contractable membrane sealingly attached to and normally disposed within said hub adjacent to said first opening, said membrane being so dimensioned as to 

